(1) Field of the Invention
The present invention relates to an apparatus and method for estimating atmospheric pressure in an internal combustion engine. In particular the invention relates to an apparatus and method for respectively detecting engine intake air flow rate as a mass flow rate and a volumetric flow rate, and then estimating atmospheric pressure (altitude) based on these flow rates and intake air temperature.
(2) Description of the Related Art
Conventionally with electronically controlled fuel injection units in internal combustion engines, it is known to respectively detect the mass flow rate of the intake air with a thermal type air flow meter, and the volumetric flow rate of the intake air based on throttle valve opening and engine rotational speed.
However, estimation of changes in atmospheric pressure (altitude) from mass flow rate detected with a thermal type air flow meter, and volumetric flow rate detected from throttle valve opening and engine rotational speed, has yet to be realized.